Competition of various LH-RH analogs and fragments with 125I-LH-RH for specific binding sites on isolated pituitary plasma membranes

Kühl, H.; Baumann, R; Sandow, J.; Taubert, H.‐D.

doi:10.1016/0303-7207(80)90104-5

Cited by 13 publications

(6 citation statements)

References 12 publications

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“…LHRHa would not have biological activity if ingested by humans even in these extreme cases, as LHRHa was digested in the simulated human stomach. Fragments of LHRHa are not biologically active in humans (Kuhl et al, 1980). Results of this study support the inference that LHRHa used as a spawning aid would not pose a human food-safety risk.…”

Section: Discussionsupporting

confidence: 80%

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In vitro digestion of luteinizing hormone releasing hormone analog (LHRHa) using simulated gastric conditions in assessing human food safety

Shang

et al. 2016

Food Chemistry

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Section: Discussionsupporting

confidence: 80%

“…Additionally, tissues containing LHRHa/GnRHa would be cooked, making their availability even less likely. Fragments of LHRHa were not biologically active (Kuhl, Baumann, Sandow, & Taubert, 1980). LHRHa is an essential therapeutic drug for treatment of human individuals with some cancers or some forms of infertility.…”

Section: Introductionmentioning

confidence: 99%

In vitro digestion of luteinizing hormone releasing hormone analog (LHRHa) using simulated gastric conditions in assessing human food safety

Shang

et al. 2016

Food Chemistry

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“…Furthermore, our calculated KDs are within the range of those described by other investigators [4,7,16,19]. In agreement with findings of Chan et al [2], adult and neonatal anterior pituitary LHRH binding sites had similar Kus, and the neonatal receptor populations consistently ap peared to possess 2 to 3-fold more binding sites per milli gram of membrane protein than the adult population.…”

Section: Discussionsupporting

confidence: 80%

Melatonin Does Not Affect Luteinizing Hormone-Releasing Hormone Binding to Neonatal Rat Anterior Pituitary Membranes

Henshel¹,

Sattler²,

Martin³

1982

Neuroendocrinology

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Melatonin suppresses luteinizing hormone-releasing hormone (LHRH)-stimulated release of luteinizing hormone (LH) and follicle-stimulating hormone from neonatal rat gonadotrophs. Since this effect occurs rapidly and selectively, we examined in this study the possibility that melatonin may inhibit LHRH-receptor binding. The physiologically active LHRH analog (D-Ala⁶, des-Gly¹⁰)-LHRH-N-ethylamide (D-Ala) was iodinated by a modification of a lactoperoxidase method and its concentration determined by self-displacement in the receptor binding assay. Crude anterior pituitary membranes from 10- to 12-day-old female rats were incubated with [¹²⁵I]iodo-D-Ala (¹²⁵I-D-Ala) either alone or in the presence of melatonin or a peptide LHRH antagonist at 4 °C in a volume of 200 µl. Specific binding was defined as the difference between the binding in the absence and in the presence of 50 or 100 µM D-Ala, as specified. Binding experiments were terminated by dilution and filtration through either Millipore EHWP or Whatman GF/C filters. Specific binding approximated equilibrium by 120 min. Scatchard analysis revealed an apparent K_D of 1.5 nM with the EHWP filters and 1.13 nM with the GF/C filters. In all experiments, use of either filter produced similar results; the only obvious difference was an apparent increase in the number of binding sites with the EHWP filters. Melatonin (1 µM) had no detectable effect on binding of ¹²⁵I-D-Ala. By contrast, the peptide LHRH antagonist at 10 and 100 nMinhibited binding of ¹²⁵I-D-Ala by 43 and 80%, respectively. However, in parallel studies with cultured anterior pituitary cells, both melatonin and the peptide antagonist inhibited the D-Ala-stimulated LH release. Melatonin (1 µM) suppressed the LH response to 10 pM D-Ala by 51%, and the peptide antagonist at 10 and 100 nM similarly inhibited release by 33 and 84%, respectively. These data clearly show that while melatonin and the LHRH peptide antagonist both suppress stimulated LH release by gonadotrophs in culture, melatonin does not antagonize the binding of D-Ala to the LHRH receptor.

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“…However, if this were the only factor involved, it should be possible to match the amplitude of the LHRH-A response by increas ing the LHRH level used, and our findings indicate that this is not possible. It appears that other factors contribute to the degree of response of E2R to the 2 hormones; this is consis tent with the inability to establish a strict co-linearity be tween parameters such as binding affinity for plasma mem brane LHRH receptors [13] or enzymatic degradation [9] of LHRH analogues, and their enhanced biological efficacy vis-a-vis LH release. An additional curious feature of our observations was the decline in activity of LHRH-A at lev els higher than the peak dosage.…”

Section: Discussionmentioning

confidence: 97%

“…This issue of a priori internalization preceding function is highly contro versial and is currently under intensive investigation for many peptide hormone systems [20], Within recent years, evidence has been forthcoming that LHRH enters anterior pituitary cells as an intact molecule, and can then be found within or attached to intracellular organelles [4]. Such ob servations have led to speculated correlations between such intracellular interactions and the release and/or synthesis of LH [13]. A damaging blow to this proposal was struck by the report of effective LH release in response to a purport edly impenetrable conjugate of LHRH [3].…”

Section: Discussionmentioning

confidence: 99%

Specific, Estrogen-Sensitive Alterations in Anterior Pituitary Cytoplasmic and Nuclear Estrogen Receptors Actuated by LHRH

Singh¹,

Muldoon²

1983

Neuroendocrinology

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We have previously demonstrated that LHRH is capable of eliciting a dramatic and direct elevation of anterior pituitary levels of nuclear estrogen receptors (E2R) [18, 24]. This action was manifest under both in vitro and in vivo conditions, and could not be attributed to an amplification of the rate or extent of cytosol E2R binding, activation or transloca-tion. In view of the implications of these observations in terms of estrogen-LHRH interplay in regulation of gonadotropin secretion, we have further explored the nature, specificity and estrogen dependency of the LHRH effect. TRH, a long-acting agonist, (D-Ala⁶, des-Gly¹⁰)LHRH-N-ethylamide (LHRH-A), and an antagonist, N-Ac-D-p-Cl-Phe¹², D-Trp³, D-Phe⁶, D-Ala¹⁰-LHRH (LHRH-ANT), were compared with LHRH for their ability to alter compartmental E2R concentrations following incubation in vitro. Either intact dispersed anterior pituitary cells or isolated cytosol and nuclei from pituitary homogenates were used as receptor source. LHRH-A and LHRH both caused a 40–60% decrease in the cytoplasmic E2R binding capacity of intact cells following incubation of 30 min at 37 °C; the magnitude of the inhibition was dose independent over a peptide range of 0.1–1000 pmol/pituitary. In contrast, TRH caused a dose-related decrease in cytosol E2R binding. When nuclear E2R levels were assessed, significant dose dependent increases were observed with both LHRH and LHRH-A treatment. The effective dose of LHRH-A was approximately an order of magnitude lower than that of LHRH. TRH, on the other hand, over a wide concentration range (0.3–3,000 pmol/pituitary), had no significant effect on specific nuclear estrogen binding. In isolated nuclei, as in the intact cell studies, LHRH and LHRH-A were stimulatory, while TRH effected no alteration of E2R binding levels. The LHRH effect could be totally blocked by LHRH-ANT. In isolated cytosol, TRH did not affect E2R binding, whereas LHRH and LHRH-A were both mildly stimulatory. The effectiveness of LHRH in enhancing nuclear E2R binding correlated directly with the endogenous estrogen titers of the animals. In tissue from ovariectomized animals primed with 0.1 μg estradiol/day, LHRH was 4 times more potent as a stimulator of nuclear E2R than in tissue from nonprimed castrate animals. If the priming dose was increased to 1.0 μg/day, a further significant increase in sensitivity of nuclear E2R to LHRH was observed over the 0.1 μg priming dose level. The results of these studies attest to the releasing hormone specificity of changes in anterior pituitary E2R levels, and to the involvement of estrogen-LHRH sensitization in this process, analogous to the well-documented estrogen-LHRH interplay in regulation of LHRH release.

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Competition of various LH-RH analogs and fragments with 125I-LH-RH for specific binding sites on isolated pituitary plasma membranes

Cited by 13 publications

References 12 publications

In vitro digestion of luteinizing hormone releasing hormone analog (LHRHa) using simulated gastric conditions in assessing human food safety

In vitro digestion of luteinizing hormone releasing hormone analog (LHRHa) using simulated gastric conditions in assessing human food safety

Melatonin Does Not Affect Luteinizing Hormone-Releasing Hormone Binding to Neonatal Rat Anterior Pituitary Membranes

Specific, Estrogen-Sensitive Alterations in Anterior Pituitary Cytoplasmic and Nuclear Estrogen Receptors Actuated by LHRH

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